Numerikus sorok - Index of
Numerikus sorok - Index of
Numerikus sorok - Index of
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✎☞<br />
✍✌ T a n , b n , c n , d n > 0<br />
⎧<br />
1. a n + b n ∼ c n + d n<br />
}<br />
a n ∼ c n<br />
b n ∼ d n<br />
=⇒<br />
⎪⎨<br />
⎪⎩<br />
2. a n b n ∼ c n d n<br />
3.<br />
4.<br />
1<br />
∼ 1 a n c n<br />
b n<br />
∼ d n<br />
a n c n<br />
Megint nincs különbség!<br />
✎☞<br />
B ✍✌<br />
a n ∼ c n : a n<br />
→ 1 =⇒ 0 < 1 − ε < a n<br />
< 1 + ε, n > N 1<br />
c n c n<br />
b n ∼ d n :<br />
Legyen n > max{N 1 , N 2 } = N<br />
b n<br />
d n<br />
→ 1 =⇒ 0 < 1 − ε < b n<br />
d n<br />
< 1 + ε, n > N 2<br />
1. 1 − ε = (1 − ε)c n + (1 − ε)d n<br />
c n + d n<br />
< a n + b n<br />
c n + d n<br />
< (1 + ε)c n + (1 + ε)d n<br />
c n + d n<br />
= 1 + ε ,<br />
ha n > N<br />
2. ¬B<br />
3.<br />
1<br />
a n<br />
1<br />
c n<br />
= c n<br />
a n<br />
= 1 a n<br />
cn<br />
→ 1<br />
4. Az előző kettőből következik: a n ∼ c n =⇒ 1 a n<br />
∼ 1 c n<br />
; másrészt b n ∼ d n<br />
=⇒ b n<br />
a n<br />
∼ d n<br />
c n<br />
✓✏<br />
Pl.<br />
✒✑a n = 3√ 2n 2 + n + 1 − 3√ 2n 2 − 3n − 7 =<br />
2n 2 + n + 1 − (2n 2 − 3n − 7)<br />
= ( √ 3<br />
2n2 + n + 1 ) 2 √ +<br />
3<br />
2n 2 + n + 1 3√ 2n 2 − 3n − 7 + ( √ 3<br />
2n 2 − 3n − 7 ) 2 ∼<br />
∼<br />
(<br />
)<br />
3√ 2 2 (<br />
2 n 3 +<br />
4n<br />
3√<br />
2 n<br />
2<br />
3<br />
) 2<br />
+<br />
(<br />
)<br />
3√ 2 2<br />
=<br />
2 n 3<br />
4n<br />
3√<br />
4 · 3 n<br />
4<br />
3<br />
=<br />
4<br />
3 3√ 4 3√ n<br />
=⇒ a n → 0<br />
✓✏<br />
Pl.<br />
✒✑a n =<br />
arctg √ n<br />
3√<br />
2n2 + n + 1 − 3√ 2n 2 − 3n − 7 ∼<br />
π<br />
2<br />
4<br />
3 3√ 4 3√ n<br />
=konst· 3√ n → ∞<br />
c○ Kónya I. – Fritz Jné – Győri S. 34 v1.4